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Subject[PATCH] ACPI: Idle C-states disabled by max_cstate should not disable the TSC
From: Len Brown <len.brown@intel.com>

Processor idle power states C2 and C3 stop the TSC on many machines.
Linux recognizes this situation and marks the TSC as unstable:

Marking TSC unstable due to TSC halts in idle

But if those same machines are booted with "processor.max_cstate=1",
then there is no need to validate C2 and C3, and no need to
disable the TSC, which can be reliably used as a clocksource.

Signed-off-by: Len Brown <len.brown@intel.com>
---
drivers/acpi/processor_idle.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
index e39a40a..e65476f 100644
--- a/drivers/acpi/processor_idle.c
+++ b/drivers/acpi/processor_idle.c
@@ -582,7 +582,7 @@ static int acpi_processor_power_verify(struct acpi_processor *pr)

pr->power.timer_broadcast_on_state = INT_MAX;

- for (i = 1; i < ACPI_PROCESSOR_MAX_POWER; i++) {
+ for (i = 1; i < ACPI_PROCESSOR_MAX_POWER && i <= max_cstate; i++) {
struct acpi_processor_cx *cx = &pr->power.states[i];

switch (cx->type) {
--
1.6.3.1.9.g95405b


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